JP5555428B2 - Radio frequency ion guide - Google Patents

Description

  The present disclosure relates to ion guides. More particularly, this disclosure relates to radio frequency (RF) ion guides used to transport ions.

  Ion guides are used in analyzers and other devices for transporting ions and for other purposes. Ions are provided using an ion source. For most atmospheric ion sources, ions pass through an opening or skimmer before entering the ion guide at the ion inlet end. A radio frequency signal may be applied to the ion guide to provide radial focusing of the ions within the ion guide. As a result, the transfer efficiency through the ion guide can be very high.

  Some ion sources, including matrix assisted laser desorption ionization (MALDI), surface enhanced laser desorption ionization (SELDI) and other ion sources are capable of generating ions in lower pressure regions. When such an ion source is used with an ion guide, the ion source can be placed adjacent to the ion entrance end of the multipole so that the ion generation region and the multipole can be maintained at the same pressure. Some of the ions generated from the ion source enter the ion guide. When there is little or no pressure difference between the source and the ion guide, the ions are typically advanced along the length of the ion guide by space charge repulsion between ions of the same polarity. It is done. As new ions are generated during a particular experiment and enter the ion guide, previously generated ions are advanced along the length of the ion guide by space charge repulsion. The space charge effect advances ions through the ion guide, but the effect can lead to a number of undesirable results. For example, the degree of axial force on ions depends on both the number and proximity of other ions of the same polarity. As a result, when space charge is the dominant driving force, the transport of ions through the ion guide is uneven and slow. For MALDI weighing experiments where the sample can be removed until it is depleted on the target, the degree of ion separation from the sample is first high and then decays to zero over the course of the experiment. Thus, the space charge force is initially strong and then decays, so that ions generated near the end of the experiment are advanced weaker through the ion guide. This can lead to rough and variable peak shapes that are not suitable for high-throughput weighing. Furthermore, since the space charge force is essentially omnidirectional, it is expected that the ion loss will be greater when the space charge force includes the most important driving force for ion movement in the axial direction.

  It is desirable to provide an ion guide with a more efficient ion transport mechanism than previous devices to transport ions more efficiently and reproducibly along the length of the ion guide.

(Overview)
In one example in accordance with the first aspect, Applicants' teachings provide a method for transporting ions in an ion guide having an ion inlet end and an ion outlet end. The method includes providing an ion focusing field in the ion guide and generating a flow of gas along at least a portion of the length of the ion focusing field including a region adjacent to the ion exit end. To do.

  In another example of this aspect, the ion guide is a multipole ion guide having at least two poles, and the ion focusing field is provided by applying a radio frequency signal to the poles.

  In another example of this aspect, the ion focusing field is generated along the axis of the ion guide and the gas flow is provided at least partially along the axis.

  In another example of this aspect, the gas flow is generated by placing a sleeve around the pole and sucking the gas through the sleeve.

  In another example of this aspect, the ion guide is formed from a plurality of conductive rings separated by interspersed insulators, each insulator sealed against an adjacent ring, and the gas flow And by sucking gas through the insulator.

  In another example of this aspect, the ion guide is comprised of a plurality of rings spaced apart from each other, and the gas flow places a sleeve around the ring and absorbs the gas through the sleeve. Is generated by

  In another example of this aspect, the generally balanced axial field is generated by applying a first RF signal to the first pole and a second RF signal to the second pole, The RF signal and the second RF signal have approximately the same magnitude, but are 180 degrees out of phase with each other.

  In another example of this aspect, the method includes generating ions from an ion source disposed adjacent to an inlet end of the ion guide, the generated ions being generated by a gas flow through an ion guide assembly. From the ion inlet end of the ion guide to the ion outlet end of the ion guide.

  In another example of this aspect, an additional gas flow is generated through the ion inlet end of the ion guide. Optionally, additional gas flow can be restricted adjacent to the ion inlet end.

  In another example of this aspect, the gas flow begins adjacent to the ion inlet end and continues through the ion outlet end of the ion guide. Optionally, the gas flow can be restricted adjacent to the ion inlet end using a lens or other restrictive element.

  An example of another aspect of applicant's teaching provides an ion guide comprising a plurality of ion focusing elements disposed about an axis and a sleeve for carrying a gas flow along at least a portion of the axis. To do.

  In another example of this aspect, the ion focusing element includes a first pole and a second pole, the first pole includes at least two first pole rods, and the second pole has at least two second poles. The two pole rods are included, and the sleeve is disposed around the first pole rod and the second pole rod.

  In another example of this aspect, the ion guide has an ion inlet end and an ion outlet end, and the sleeve extends between the ion inlet end and the ion outlet end.

  In another example of this aspect, the ion guide comprises a sleeve cap that is attached to a sleeve adjacent to the ion inlet end, the sleeve cap having a cap opening aligned with the shaft.

  In another example of this aspect, the ion focusing element includes a plurality of rings separated by an insulator, which ring and insulator together form a sleeve.

  In another example of this aspect, the ion focusing element includes a plurality of rings disposed about the axis and disposed within the sleeve.

  An example of another aspect of applicant's teachings is an ion guide assembly having an ion entrance end and an ion exit end, wherein the ion guide assembly is disposed about an axis and along at least a portion of the axis. An ion guide assembly is provided that includes a sleeve for carrying a gas flow and a suction device for sucking the gas through the sleeve.

  In another example of this aspect, the ion guide assembly includes a sleeve cap that is attached to a sleeve adjacent to the ion inlet end.

  In another example of this aspect, the ion guide is placed in a differentially pumped region of the mass spectrometer so that the additional gas flow causes a pressure difference between the two vacuum stages. As a result, it is generated in the ion guide inlet.

  These and other aspects of applicant's teachings are described in more detail below.

  Several examples will now be described in detail with reference to the drawings, wherein like elements are identified with like reference numerals.

(Example description)
Reference is first made to FIGS. 1 and 2, which illustrate a first example ion guide 100. The ion guide 100 includes a mounting bracket 102, four rods 104a to 104d, a gas channeling sleeve 106, and a pair of insulators 108 and 109. The ion guide 100 has an ion inlet end 110 and an ion outlet end 112.

  The mounting bracket 102 has a base flange 114 and a barrier flange 116. In this example, the base flange 114 and the barrier flange 116 are formed integrally with the mounting bracket 102 and separated by the sleeve support 120. The sleeve support 120 has a generally cylindrical inner wall 122.

  The sleeve support 120 includes a plurality of sleeve positioning arms 124. The sleeve 106 is disposed within the sleeve support 120 and fits snugly within the inner wall 122. The sleeve 106 has a detent 126 formed around its outer periphery. The detent 126 is placed against the sleeve positioning arm 124 so that the sleeve 106 is spaced from the base flange 114 at the ion exit end 112 of the ion guide 100. The detent 126 ensures proper positioning of the sleeve 106 and rods 104a-d relative to the base flange. The sleeve 106 is fixed in place using a set screw (not shown). The set screw is threaded into the sleeve support 120 through the threaded opening to engage the sleeve. Those skilled in the art understand that a set screw is used to hold the sleeve 106 in a fixed position relative to the bracket 102.

  The sleeve 106 has a circular cross-section (when viewed in the XY plane), matches the cross-section of the inner wall 122, allows the sleeve 106 to fit snugly within the sleeve support 120, and is centered on the ion guide shaft 113. Can be adjusted. A sleeve 106 surrounds the rod 104.

  In another exemplary ion guide, the sleeve may be attached within or to the support bracket in another manner that does not use a detent or support arm to position the sleeve. For example, the sleeve may be fixed at a specific position within the support bracket. In another embodiment, the sleeve may be secured to the attachment point of the bracket, and the sleeve and bracket may not have a friction fit mount. In another embodiment, the sleeve can be attached around the multipole in any manner appropriate to that embodiment.

  Insulators 108 and 109 are mounted within sleeve 106. Insulators 108 and 109 have a series of fixation openings 128 that are shaped to pass through the insulation and receive fixation screws 130. The mounting bracket 102 and the sleeve 106 have corresponding openings 132 and 134 that allow the fixed opening 128 to be accessed. Rod 104 is attached to insulators 108 and 109 using screws 130. Rod 104 is threaded to accept screw 130. Insulators 108 and 109 are not electrically conductive and serve to electrically insulate rods 104 from each other.

  In this example, insulators 108 and 109 are held in place within sleeve 106 by friction. In another exemplary ion guide, insulators 108 and 109 may be secured to the inner surface of sleeve 106 using fasteners such as screws, bolts, or adhesives.

  Rods 104a-d form a quadrupole and operate as an ion focusing element. Other ion guides that use a gas channeling sleeve may include five or more rods. Such an example and the rod in this example form a multipole. In this example, the rod 104 is disposed equidistant from the multipole shaft 113 and parallel thereto, but may be attached by any means known in the art. The rods 104a and 104c are arranged opposite to each other around the axis 113 and define the X axis. Similarly, rods 104b and 104d are disposed opposite to each other about axis 113 and define a Y axis that is perpendicular to the X axis. The Z axis is defined perpendicular to both the X and Y axes. The axis 113 is on the Z axis. In this example, the rods 104 have a circular cross section and each rod has an axis. The axis of the rod 104 defines a square when viewed in a cross section taken perpendicular to the Z axis.

  The rod 104 has a circular cross section. The present disclosure is not limited to use with cylindrical rods, but can be used with rods of any cross-section such as parabolic rods, square rods or hyperbolic rods.

  The rods 104a and 104c are electrically connected together and together form an X pole. (The connection is not shown in the figure. In one example, the electrical connector is attached between one of the screws 130 used to attach each rod and the connector connected to the wire and connecting the rod). . The rods 104b and 104d are electrically connected together to form a Y pole.

  The X and Y poles are coupled to an RF signal source (not shown) that applies an RF signal to the pole. The RF signal is configured to provide an ion focusing field along the length of the ion guide. The RF signals have approximately equal magnitude, but are 180 ° out of phase with respect to the pole, providing a balanced RF field along the quadrupole axis 113. Alternatively, an unbalanced RF signal can be applied to the pole.

  The bracket 102 is made from a gas impermeable material. In this example, the bracket 102 is made from stainless steel. In other examples, the bracket 102 may be made from another metal or a gas impermeable material such as plastic or nylon. The bracket 102 has a plurality of openings 118 adjacent to the base flange 114. The exit plate 158 is attached to the bracket 102 adjacent to the ion exit end 112 of the ion guide. The exit plate 158 has an ion exit opening 160 through which ions can exit the ion guide 100. The ion outlet opening 160 is centered on the axis 113.

  Referring to FIG. 3, FIG. 3 illustrates the ion guide 100 mounted within the housing 140 and forming the ion guide assembly 139. The housing 140 has a mounting flange 142 that uses the mounting opening 141 to place the housing 140 in or on an ion processing device such as an ion source or mass spectrometer (or both). Can be used to attach. The housing 140 also includes an ion guide seat flange 144, an ion guide chamber 146, a pump port 148, and a pump mounting flange 150. The ion guide 100 is inserted into the ion guide chamber 146 and the base flange 114 is disposed relative to the seat flange 144. An o-ring (not shown) made from a suitable material such as Viton can be used to achieve a vacuum seal. The ion guide chamber 146 has a circular cross section and is sized to receive the ion guide mounting bracket 102.

  The pump flange 150 is adapted to receive a gas tube 153 (FIG. 4), which can be used to draw gas from a roughing pump 154 (FIG. 4) or pump port. Connected to the suction device. Alternatively, the suction device can be connected directly to the pump flange 150. In this example, the gas pipe 153 is connected to the pump flange 150 using a plurality of screws. In other embodiments, any other securing device, such as screws, clips, adhesives, hose clamps, or interference mounts can be used to attach a roughing pump or other suction device.

  The volume of space that extends from the ion inlet end 110 of the ion guide to the ion outlet end 112 and is contained within the sleeve in which the rod 104 is located may be referred to as the ion transport space 156. The opening 118 connects the ion transport space 156 and the ion guide chamber 146 so that gas can flow between them. The pump port 148 is connected to the ion guide chamber 148.

  When the roughing pump 154 is attached to the housing 140 and activated, the roughing pump 154 draws gas in the pump port 146 from the ion guide assembly, creating a gas flow 157 that begins at the ion inlet end 110, The gas flow passes through the ion exit end 112, the opening 118, the ion guide chamber 146, and the pump port 148 and out of the ion guide assembly through the roughing pump. Along the length of the ion guide 100, the gas flow 157 enhances ion transport from the ion inlet end 110 to the ion outlet end 112. Ions are focused by the RF field applied to the rod 104 and therefore do not follow the gas flow 157 over the ion exit end 112. The ions continue their motion along the axis 113 and exit the ion guide through the ion exit opening 160.

  Referring to FIG. 4, FIG. 4 illustrates an ion guide assembly 139 used with a MALDI (Matrix Assisted Laser Desorption Ionization) ion source 164 and an ion processing device 166. The MALDI ion source 164 includes a sample plate 170, a matrix solution 172, and a laser 174. A sample containing molecules that are ionized and transported through the multipole assembly 139 is combined with a matrix base. The sample and matrix solutions are mixed to form a matrix solution 172, which is then deposited on the sample plate where the sample and matrix co-crystallize. Alternatively, the sample can be deposited on a suitable surface that does not require a matrix base.

  The ion processing device 166 is mounted adjacent to the ion outlet opening 160 at the base flange 114. The ion processing device 166 is an ion analysis device or ion processing device such as an ion detector, mass analyzer (which may include an ion detector) or a combination of ion selection, ion processing or ion detection stages. It can be of any type.

  The multipole assembly 139 is used as follows.

  The RF signal source is activated and applies RF signals to the X and Y poles. The applied RF signal typically creates a converging field along the multipole axis 113.

  The roughing pump 154 is activated and provides a gas flow 157. The RF signal source and roughing pump 154 may remain in operation between experiments. After the signal source and roughing pump are activated, the individual experiments are performed as follows.

  Laser 174 is activated to perform individual experiments. When the laser 174 is activated, the laser 174 emits a laser beam 178 to the matrix solution 172. The sample in the matrix solution 172 is ionized and ions originating from the sample begin to flow into the multipole assembly at the ion inlet end 110. Ion flow from the target plate to the multipole assembly is facilitated by the application of an electric field between the plate and the inlet. The flow of ions through the ion transport space 122 is due in part to the aforementioned space charge repulsion and is enhanced by the gas flow 157.

  The RF signal applied to the X and Y poles causes at least some of the ions entering the multipole assembly to converge radially along the multipole axis. These focused ions are drawn along the length of the ion guide 100 to the ion exit end 112 and are ejected into the ion processing device 166.

  A series of experiments can be performed by repeatedly starting and stopping the laser 174 and / or moving the sample plate.

  Reference is now made to FIG. 5, which illustrates a mass spectrum 180 generated using the configuration of FIG. 4 with a mass spectrometer used as the ion processing device 166. The mass spectrometer includes an ion detector, and for this example, the mass analyzer is operated in a selected reaction monitoring mode of operation. Ions reaching the detector are counted and the mass spectrum 180 plots ions that are counted (cps) per second by the ion detector over time. The mass spectrometer may include various ion selection stages that allow a collision cell or only selected ions to be transported through the stage. When ions are selected in the mass spectrometer, the ions reach the ion detector, and specific ions can be selected and counted. Optionally, a DC offset can be applied to the MALDI sample plate 170 or the rod 104, or both, to enhance ion entry into the ion transport space.

  Mass spectrum 180 illustrates the count of haloperidol fragment ions that reach the ion detector over time during several consecutive experiments. A sample of haloperidol is mixed with a matrix base to form a matrix solution 172. Multipole assembly 100 is activated by activating RF signal source and roughing pump 154. Each test is performed by starting the laser 174 for a period of time and then stopping the laser.

  Four peaks 182 corresponding to the data generated for separate samples of haloperidol were generated within about 0.3 minutes as shown in mass spectrum 180. Each of the peaks has a peak width 182w (for this purpose, defined as the period from the start of the peak until the ion count per second drops below 5000). In addition, each peak has a tail 182t (defined as the period of time after which the ion count drops back to 0 after every time the ion count drops below 5000).

  Referring now to FIG. 6, FIG. 6 illustrates a mass spectrum 190 generated using a known ion transport multipole assembly (not shown) that does not include a sleeve. Prior art multipole assemblies include a roughing pump that reduces the pressure in the multipole assembly. Prior art multipole assemblies also include a signal source for applying an RF signal to the poles of the multipole. Three peaks 192 of the count of ions corresponding to the haloperidol fragment are shown in the mass spectrum 190 as obtained over the same time frame.

  To generate mass spectra 180 and 190, laser 174 was activated for the same time at the beginning of each test. Subsequent tests were initiated when ions from previous tests were no longer counted by the ion detector.

  Referring to FIGS. 5 and 6 together, mass spectra 180 and 190 can be compared. The peak 192 of the mass spectrum 190 has a peak width 192 w wider than the peak width 182 w of the peak 182 in the mass spectrum 180. The peak tail 192t of the mass spectrum 190 is also longer than the peak width 182t of the peak 182 in the mass spectrum 180. The total peak length (which combines the peak width with the tail width) is much shorter for peak 182 than for peak 192. The height of peak 182 is about 120,000 cps compared to the height of about 50,000 cps for peak 192. Finally, peaks 182 are very similar to each other. In comparison, the peak 192 is not similar and in fact is quite different, especially in the tail period.

  The use of a gas channeling sleeve is frequently generated, with peak 182 narrower (in peak width, tail length and overall length) than peak 192, much larger in peak height, reproducible in terms of area and shape. Makes it possible to Further, the shape of peak 182 is more consistent than peak 192 and is repeatable. The use of a gas channeling sleeve allows higher throughput of ions through the ion guide, as shown by peaks 182 that are higher, narrower, and closely spaced than peak 192 in mass spectrum 190.

  Optionally, a gas source can be used to provide gas at the ion inlet end 110 of the ion guide. Such gas is drawn through the ion transport space as part of the gas stream 157. Providing such a gas flow enhances the gas flow 157 and increases the axial resistance to ions in the ion transport space, thereby causing ions from the ion inlet end 110 to the ion outlet end 112. Carry more efficiently.

  Gas channeling techniques can be used in ion guides operating at any pressure level. The technique is particularly useful with ion guides that operate at pressures of 0.1 Torr or higher. However, the technique can be used with lower pressure ion guides.

  Reference is now made to FIG. 7, which illustrates a second exemplary ion guide 200. The ion guide 200 includes a sleeve cap 209 that is attached to the sleeve 206 at the ion inlet end of the ion guide. In this example, the sleeve cap 209 has a conical shape. In another example of an ion guide assembly according to the present invention, the sleeve cap is a different shape and may be a flat cap that extends across the sleeve 206 at the ion inlet end of the ion guide 200.

  Ions enter the ion transport space 256 from the ion source. Further, the gas flow 257 begins at the cap opening 209. The sleeve cap 209 restricts the flow of gas into the ion inlet end 210 and when a roughing pump (or another suction device) is used to set the pressure in the ion transfer space, the pressure differential is Allowing it to be created between the ion transport space 256 and the MALDI ionization region (between the MALDI plate and the ion inlet end of the ion guide and the adjacent matrix solution). For example, the gas may be evacuated into the ionization region, allowing a higher pressure type in the ionization region that may exist in the ion transport space 256.

  The sleeve cap 209 may also serve to enhance gas flow through the cap opening 209 by increasing the gas resistance near the point of ion removal adjacent to the matrix solution 244. The number of ions entering the ion transport space 256 can be increased by the increased gas resistance. The cap may also take the form of a cone that is placed (but not fixed) in front of the ion guide assembly, separating the pressure differential areas. In these situations, the gas expands through the cone and enters the ion guide inlet, and the sleeve supplements this flow along the entire length of the ion guide.

  Reference is now made to FIG. 8, which illustrates another exemplary ion guide 300. The ion guide 300 includes a plurality of ion focusing rings 304 that are spaced apart from one another. An RF signal source (not shown) applies a first RF signal to the first group of rings 304 and a second RF signal to the second group of rings 304. In this example, the rings are placed alternately in the first and second groups so that each adjacent pair of rings in the first group has a ring from the second group between them. Have. The reverse is also true. The first and second RF signals are configured to focus ions along the axis 313 of the ion guide. A sleeve 306 is disposed in the mounting bracket 302. Insulator 308 is attached to sleeve 306 and ring 304 is attached to insulator 308. Insulator 308 may be attached to sleeve 306 and ring 304 using friction or mechanical or adhesive fasteners (not shown). The ion guide 300 is installed in a housing to form an ion guide assembly to which an aspiration device can be coupled. The ion guide 300 is used in the same manner as the ion guide 100 and transfers ions from the ion inlet end 310 to the ion outlet end 312. When the suction device is activated, the sleeve 306 carries a gas flow 357 generally along the axis 313. The ring has an additional DC offset to further facilitate ion motion in addition to gas flow.

  Reference is now made to FIG. 9, which illustrates another exemplary ion guide 400. Similar to ion guide 300, ion guide 400 uses ion focusing ring 404 to focus ions along the axis of the ion guide. Rings 404 are separated by an insulator 408 attached between the rings to electrically insulate adjacent rings. Ring 404 and insulator 408 form a cylinder that is sealed and gas impermeable along the sidewalls. Ring 404 and insulator 408 are attached to the mounting bracket using a non-conductive plate 409. The gas impermeable sidewall serves as a gas channeling sleeve 406 and does not require a separate sleeve. The ion guide 400 is mounted within the housing and forms an ion guide. The suction device is used to provide a gas flow 457 along the length of the ion guide 400. The gas flow transfers ions from the ion inlet end 410 to the ion outlet end 412.

  Several examples have been described. The particular structure of the ion guide using a gas channeling sleeve can be altered by the structure and operation of the device with which the ion guide is used.

  In other examples similar to the ion guide 200, the sleeve cap may be formed integrally with the sleeve 206. Similarly, a sleeve cap can be used in connection with the sleeve 306, and the sleeve cap can be attached to the side wall 406 in the ion guide 400. Alternatively, the ion guides 100, 200, 300, and 400 can be placed behind an opening or cone that restricts gas flow.

  The gas flow generated in the ion guide using the gas channeling sleeve increases the flow of additional gas resulting from space charge repulsive effects, or gas expansion, and into the ion guide inlet, and the ion flow through the multipole assembly. Strengthen the flow. The ion transport gas flow can also be used in conjunction with other mechanisms that can enhance or direct ion transport. For example, tilted rods or resistive rods can be used to create a non-constant field along the length of the multipole assembly. Application of the RF signal to the rod may also enhance ion transport along the multipole assembly. In such embodiments, the RF signals applied to the first and second poles may not be of equal magnitude and may not be 180 degrees out of phase with each other. The use of a gas channeling sleeve can be shared with these and other ion transport structures and techniques.

  The ion guides 100 and 200 are described with respect to a quadrupole. The gas channeling sleeve has more than five rods and can be used with any multipole assembly that can have more than two poles.

  The examples described so far are illustrated primarily in the context of an ion source that does not provide a gas flow within the ion transport space. The technology is also suitable for use with ion sources that provide ions in a gas stream, such as an electrospray ion source. Electrospray ion sources inject ions into a gas stream that transports the ions. The gas stream transports ions along the axis of the ion guide over at least a portion of the length of the ion guide. By generating additional gas streams using the present invention, the transport of ions from such ion sources can be enhanced.

  Various other modifications and changes may be made to these exemplary embodiments without departing from the spirit and scope of applicant's teachings, which are within the scope of the appended claims. Limited only by.

FIG. 1 is a perspective view of an ion guide of a first example. FIG. 2 is a perspective sectional view of the ion guide of the first example. FIG. 3 is a perspective sectional view of the first ion guide assembly. FIG. 4 is a cross-sectional side view of the first ion guide assembly in use. FIG. 5 is an example mass spectrum generated using the ion guide assembly of the first example. FIG. 6 is an example mass spectrum generated using a prior art ion guide. FIG. 7 is a perspective sectional view of the ion guide of the second example. FIG. 8 is a perspective sectional view of the ion guide of the third example. FIG. 9 is a perspective sectional view of the ion guide of the fourth example.

Claims (19)

A method for transporting ions comprising:
The method
Providing an ion guide within a single pressure region, the ion guide having an ion inlet end and an ion outlet end;
Providing an ion focusing field within the ion guide;
Disposing a gas channeling sleeve around the ion guide;
By sucking the gas through the gas channeling sleeve includes the fact that from the ion entrance end to a region adjacent to said ion exit end along said ion focusing field to generate a flow of gas, the method .   The method of claim 1, wherein the ion guide is a multipole ion guide having at least two poles, and the ion focusing field is provided by applying a radio frequency signal to the poles.   The ion guide is formed from a plurality of conductive rings separated by interspersed insulators, each insulator being sealed against an adjacent ring, and the flow of gas to the ring and the insulator. The method of claim 1, wherein the method is generated by aspirating gas through.   The ion guide is composed of a plurality of rings that are spaced apart from each other, and the gas flow is arranged such that the gas channeling sleeve is arranged around the ring, and gas is passed through the gas channeling sleeve. The method of claim 1, wherein the method is generated by aspiration.   The pole includes a first pole and a second pole, and the ion focusing field applies a first RF signal to the first pole and a second RF signal to the second pole. The method of claim 2, wherein the first RF signal and the second RF signal have substantially equal magnitudes but are 180 degrees out of phase with each other. The ion guide wherein ions inlet end further includes a generating ions from an ion source which is positioned adjacent to the, the generated ions by the flow of the gas, ion entrance end of the ion guide from being transported toward the ion exit end of the ion guide method according to claim 1.   2. The method of claim 1, further comprising generating ions at an elevated pressure relative to the ion guide and passing the ions through one or more pressure differentiation elements prior to entering the ion guide. The method described.   The method of claim 1, wherein an additional gas flow is generated through the ion inlet end of the ion guide. 9. The method of claim 8 , wherein the additional gas flow is restricted at the ion inlet end.   The method of claim 1, wherein the gas flow is generated through the ion inlet end of the ion guide. The method of claim 10 , wherein the gas flow is restricted at the ion inlet end. An ion guide,
(A) a plurality of ion focusing elements disposed about an axis;
(B) an ion inlet end and an ion outlet end that are spaced along the axis;
(C) a gas channeling sleeve for carrying a gas flow along the axis from the ion inlet end to a region adjacent to the ion outlet end , wherein the ion guide is within a single pressure region; A gas channeling sleeve disposed;
And (d) through the gas channeling sleeve and a suction device for sucking a flow of the gas, the ion guide. The ion focusing element includes a first pole and a second pole, the first pole includes at least two first pole rods, and the second pole includes at least two second poles. 13. The ion guide of claim 12 , comprising a rod, wherein the gas channeling sleeve is disposed about the first pole rod and the second pole rod. Said ion guide comprises an ion inlet end and the ion exit end, said gas channeling sleeve extends between said ion inlet end and the ion exit end, the ion guide of claim 13. Further comprising a sleeve cap mounted on said gas channeling sleeve adjacent said ion inlet end, the sleeve cap has a cap aperture to allow the ions entering the ion guide of claim 14 ions guide. The ion guide of claim 12 , wherein the ion focusing element includes a plurality of rings separated by an insulator, the rings and the insulator together forming the gas channeling sleeve. The ion guide of claim 12 , wherein the ion focusing element includes a plurality of rings disposed about the axis and disposed within the gas channeling sleeve. An ion guide assembly having an ion inlet end and an ion outlet end comprising:
(A) a plurality of ion focusing elements disposed about an axis;
(B) a gas channeling sleeve for carrying a gas flow along the axis from the ion inlet end to a region adjacent to the ion outlet end ;
(C) an aspiration device for aspirating gas through the gas channeling sleeve, wherein the ion guide assembly comprises an aspiration device disposed within a single pressure region assembly. The ion guide assembly of claim 18 , further comprising a sleeve cap attached to the gas channeling sleeve adjacent to the ion inlet end.

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